Effects of development on wildlife

Authors(s): W. Clark and R. Wiseman

Publication: Effects of winter recreation on wildlife of the Greater Yellowstone Area: a literature review and assessment. Report to the Greater Yellowstone Coordinating Committee. Yellowstone National Park, Wyoming.

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Publication Date: 0000-00-00

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Abstract: Increasing human development has a variety of impacts on wildlife and their habitats. The effects of development may act as additional adverse impacts to wildlife populations already affected by human activity. This may be important during winter when many wildlife populations are already nutritionally and energetically stressed. The term ?development? is most frequently used in reference to new home-building: subdivisions, ranchettes, and second homes. While this activity is possibly the most important factor affecting western wildlife, other types of development impact wildlife and habitats as well. For example, conversion of former wildlife habitat to agricultural use or livestock grazing land where wildlife is excluded and the construction of new roads or the expansion of existing road networks that create unsuitable habitats for wildlife are both types of development that may have important consequences for wildlife. Development, therefore, can be defined as any human activity that permanently reduces or removes habitat that is currently available to wildlife. DEVELOPMENT IN THE GREATER YELLOWSTONE ECOSYSTEM Although more than 80 percent of the Greater Yellowstone Area (GYA) is in public ownership, the approximately 20 percent of the area that is in private ownership (about 3 million acres) contains some of the area?s most important wildlife habitats. These lands include ungulate winter ranges, riparian areas, and wetlands (Harting and Glick 1994). Since 1990, the region has experienced an overall growth rate of 12 percent, with some counties experiencing growth rates as high as 50 percent (Glick et al. 1991). As a result, home-building on rural private lands has increased tremendously (Glick et al. 1991), and nearly one-third of the region?s private acres have been subdivided (Rasker and Glick 1994). As more people settle in the area, existing roads are increasingly unable to accommodate the larger volumes of traffic, and roads are often widened or new roads are built to link areas of development and use (Glick et al. 1998). The region?s increasing population also contributes to increasing human use of the region?s natural areas. For example, an estimated 25 percent of all visitors to Yellowstone National Park in 1990 were residents of the surrounding three states (National Park Service 1998). GENERAL IMPACTS OF DEVELOPMENT ON WILDLIFE DIRECT MORTALITY Many human uses of developed landscapes are incompatible with wildlife use or presence and may result in direct mortality of wildlife that attempt to occupy those areas. Ungulates attempting to use historic winter range that has been converted to grazing land or agricultural use may not be tolerated because they compete with livestock for forage or cause damage to crops. Consequently, hunting seasons and/or areas may be designed to eliminate wildlife from those areas, or wildlife may be killed in special management actions. Large carnivores, such as bears and wolves, are generally not tolerated in proximity to areas of human habitation or use. Collisions with vehicles may also be a significant source of mortality for some wildlife populations. Between 1989 and 1995, an average of 117 wild animals were killed annually in vehicle collisions in Yellowstone National Park (Gunther et al. 1997). Severe winters may increase the number of road kills when wildlife seek lower elevation, low-snow areas, which are where roads tend to be built. Many animals also use roads and groomed trails as travel corridors when snow becomes deep and restricts movement. During the last ten years more than a dozen animals, including bison, coyotes, elk, and moose, have been killed in collisions with snowmobiles in Yellowstone National Park (M. Biel, Yellowstone National Park, personal communication). REDUCTION OR ELIMINATION OF WINTER RANGE Most ungulate species in the Rocky Mountain West rely on distinct summer and winter ranges, taking advantage of seasonally available forage at higher elevations during the summer and returning to areas of lower snow accumulation during the winter where there is greater access to forage. These low-elevation winter ranges, however, tend also to be favored by humans for settlement, agriculture, and road-building (Glick et al. 1998). Human occupation of winter home ranges may lead to decreased reproduction or increased mortality of ungulates that traditionally use those areas by decreasing the amount or quality of forage or by increasing disturbance levels (Mackie and Pac 1980, Houston 1982, Smith and Robbins 1994). Because ungulates tend to concentrate in areas of limited size during the winter, loss or degradation of even small portions of winter range have consequences far greater than loss of similarly sized portions of summer range (Mackie and Pac 1980). FRAGMENTATION OF HABITATS AND POPULATIONS Development frequently has the effect of fragmenting formerly large or widespread populations into smaller sub-populations isolated from one another to varying degrees. Fragmentation may also mean that connections to supplemental habitats or seasonal ranges are degraded or lost (Wilcove et al. 1986, Dunning et al. 1992). The ability of individuals to recolonize areas or supplement declining populations may be lost when habitat connections between sub-populations are degraded or severed (Wilcove et al. 1986). Because of these factors, populations in isolated natural areas tend to be small (Wilcove et al. 1986, Dunning et al. 1992). Small population size and lack of habitat options generally result in a lowered ability to withstand disturbance or natural environmental fluctuations and can result in local extinction of wildlife populations (Wilcove et al. 1986). DISTURBANCE Increasing numbers of humans present in the region have meant an increasing amount of human activity in areas used by wildlife. Human activity may prevent some wildlife species from taking advantage of foraging opportunities within their home ranges, even where habitats remain intact. Green (1994), for example, found that roads and traffic in Yellowstone may diminish or prevent bear use of some winter-killed ungulate carcasses. Disturbance that occurs in winter or other periods of energetic stress can be of particular concern. During the winter, many animals reduce their activity, and therefore energy expenditure, to compensate for reduced energy intake, a result of limited quantity and quality of available forage (Telfer and Kelsall 1984). Aune (1981) found that elk, bison, mule deer, and moose in Yellowstone National Park developed crepuscular activity patterns and showed altered patterns of movement and habitat use in response to winter recreationists. Behavioral and physiological responses to continuing harassment in the form of noise or certain types of human presence can shift an animal?s energy balance so that more is expended than is taken in, which results in decreased survival or reproduction success (Anderson 1995). OTHER IMPACTS In addition to the examples listed above, development can have a variety of other impacts on wildlife. Subdivisions, agricultural areas, clearcuts, or roads can block migration or movement routes, resulting in the inability of animals to reach important habitat components such as breeding or nesting areas, seasonally available forage, or refuges from predation or disturbance (Wilcove et al. 1986, Dunning et al. 1992). Development can alter habitats making them more favorable for generalist species that out-compete specialists in their former habitats. White-tailed deer, for example, appear to be replacing mule deer near developed areas in the Gallatin Valley (Vogel 1989). Although attempts have been made in recent years to restore the role of fire in natural areas, the presence of nearby human developments means that fire suppression will continue on large portions of many protected areas. Long-term fire suppression leads to changes in vegetation, which may impact wildlife in diverse ways (Houston 1982). Ground disturbance by humans has increased the presence and distribution of various species of exotic vegetation that may out-compete important native forage species. Cheatgrass (Bromus tectorum), for example, has invaded large portions of western rangelands. While this species greens early and may be of some spring forage value to ungulates, it may ultimately reduce the availability of winter forage by out-competing other, later maturing species (Houston 1982). IMPACTS TO INDIVIDUAL SPECIES ELK Humans are increasingly occupying elk winter range in the GYA. In the Jackson Hole area in the early part of this century, human occupation of elk winter range contributed to the death by starvation of thousands of elk in the valley (Anderson 1958, Robbins et al. 1982). Actions taken to mitigate for human usurpation of winter range, however, have created other problems and led to complex management issues requiring often controversial solutions. In 1912 Congress set aside a portion of the remaining valley bottom as the National Elk Refuge, and in the 1950s winter feeding of elk on the refuge and on other state-run feedgrounds in Wyoming became policy (Anderson 1958). Because the available winter range is restricted in size and the feeding program was designed to maintain a relatively high elk population, a sometimes controversial hunting program designed to control the size of the elk population was necessary (Smith and Robbins 1994). Maintaining a large number of elk in a geographically restricted area has also contributed to the continued presence of brucellosis in the herd (Thorne et al. 1991). Brucellosis in cattle has been the subject of an intensive state and federal eradication program, and the presence of the Brucella abortus bacteria in wildlife in the GYA has been the subject of much controversy in recent years, complicating management of both bison and elk. Elk in the northern portion of the GYA do not present such perplexing management problems, but are nevertheless faced with decreasing availability of winter range. Historical accounts indicate that large numbers of elk wintered in the Yellowstone River valley north of Gardiner, Montana, and summered in the mountain ranges north of the park (Houston 1982). Settlement and agricultural development in the valley bottom have reduced the number of elk that are year-round residents in this area to slightly more than 1,000 animals. These animals winter along the margins of the valley (Houston 1982). In recent years, range expansion of the northern Yellowstone elk herd during the winter has been of some concern to wildlife and land managers (T. Lemke, Montana Fish, Wildlife and Parks, personal communication) and private landowners. During some winters, elk use both public and private lands designated for summer livestock grazing, lessening the forage available to cattle. In severe winters, elk often depredate winter hay stores on private lands in the valley bottom. Any factors decreasing the quality or availability of the winter range on public lands and protected areas will only increase the magnitude of these problems and increase pressures on the elk population. BISON Bison management in the GYA has been the subject of major controversy, largely because both the Yellowstone and the Jackson bison herds have been exposed to brucellosis. Brucellosis is a disease of cattle that has been the subject of an intensive state and federal eradication program since the 1930s. Because neither Yellowstone nor Grand Teton national parks encompass a complete ecosystem for most ungulates, including bison (Keiter 1991), animals migrate out of the parks in the winter. Historically, during severe winters, Yellowstone bison probably migrated to lower elevation winter ranges in the Yellowstone River valley north of the park (Meagher 1973) and, possibly, also to winter ranges in the Madison Valley. The bison population in Yellowstone was driven to near-extinction by the beginning of the twentieth century (Meagher 1973), and during the subsequent decades when the population was recovering and heavily managed, most of the historic winter range outside the park boundary was settled and developed by humans. Much of the land adjacent to the parks is used for cattle grazing and ranching for all or part of the year. Because of the concern that infected or exposed bison could transmit brucellosis to cattle (Thorne et al. 1991) and because bison may compete with cattle for forage or destroy fences or other private property, a very complex and controversial set of management plans and policies have evolved for Yellowstone?s bison. Bison from Grand Teton National Park migrate to the National Elk Refuge and take advantage of the winter feed provided for elk. Both elk and bison on the refuge have been exposed to brucellosis, and concerns exist regarding potential contact between bison and nearby cattle (Thorne et al. 1991). The result, as in Yellowstone, is a controversial management scenario that continues to be the subject of debate and discussion. MULE DEER Mule deer populations in portions of the GYA have declined dramatically in recent years, and human development on winter range may be a contributing factor. Mule deer numbers declined as subdivisions and human activity increased on historic winter range northeast of Bozeman, Montana (Mackie and Pac 1980, Vogel 1989). Individual mule deer, particularly adult does, exhibit a high degree of fidelity to the same seasonal home ranges (Garrott et al. 1987, Mackie and Pac 1980). Because of this, it has been estimated that loss of one square mile of primary winter range along the foothills of the Bridger Range could result in loss of up to 30 percent of the southern Bridger Range mule deer population (Mackie and Pac 1980). Disturbance associated with increased housing development may cause deer to become more nocturnal (Vogel 1989, Dasmann and Taber 1956). This shift in activity pattern could increase energetic demands on deer and other animals during winter when they are nutritionally and energetically stressed by causing them to forage during colder and more severe nighttime weather (Aune 1981, Vogel 1989). Impacts may differ between migratory and resident herds. Nicholson et al. (1997) found that migratory mule deer are much more vulnerable to human disturbance than are resident animals. This may have serious implications for other migratory ungulates as well, including elk that migrate in and out of Yellowstone and Grand Teton national parks. PRONGHORN The northern Yellowstone pronghorn herd, at present numbering roughly 250 animals, is a remnant of a population that historically occupied the Yellowstone River Valley between Gardiner and Livingston, Montana (Barmore 1980). This herd may have been contiguous with pronghorn populations farther east in Montana. Pronghorn were eliminated south of Livingston prior to 1920 (Skinner 1922, Nelson 1925). Consequently, the Yellowstone pronghorn population is isolated. It is estimated that the herd has approximately 18 percent chance of extinction in the next 100 years (Goodman 1996) because of its small size and complete isolation from other pronghorn populations. Currently, pronghorn in Yellowstone have limited access to private lands north of the park boundary and, therefore, little buffer against severe conditions that occur at times within the park. Severely limited winter range may have contributed to a recent decline in numbers in this population. The Jackson Hole segment of the Sublette Antelope Herd may be at risk from development. This population segment exhibits seasonal migrations from Grand Teton National Park south to Interstate 80 near Rock Springs, Wyoming. Oil and gas development on critical winter ranges of these antelope, coupled with increasing pressure on naturally restricted migration corridors, threatens such movement (Doug McWhirter, personal communication). MID-SIZED CARNIVORES (MARTEN, LYNX, AND WOLVERINE) Mid-sized carnivores, such as marten, lynx and wolverine, are particularly vulnerable to the effects of habitat fragmentation. The current presence and distribution of lynx and wolverine in the GYA is likely influenced by development and habitat fragmentation that is the result of logging and road-building. The patches of habitat remaining may not be of sufficient size to guarantee an adequate prey base to sustain populations of these species (Buskirk and Ruggiero 1994, Lyon et al. 1994). The quality of smaller habitat patches may also be degraded as a result of influences from edge species and other disturbances occurring at or near patch boundaries (Wilcove et al. 1986). Marten, and to some extent lynx, require significant amounts of late successional stage (old-growth) forest components in their home ranges (Buskirk and Ruggiero 1994, Lyon et al. 1994). The appearance of early successional stage vegetation and structure in a mature forest that is a result of logging or subdivisions combined with easier access via summer roads or groomed snowmobile trails may increase the number of generalist predators, such as bobcats and coyotes, that compete with marten, lynx, and wolverine (Lyon et al. 1994). Dispersal and migration of marten may be largely dependent on the presence of heavily vegetated riparian areas or connected patches of mature forest (Lyon et al. 1994). Development of any kind may alter or remove these corridors, isolating populations, decreasing stability of the prey base (Buskirk and Ruggiero 1994), and increasing vulnerability to environmental pressures. Disturbance by humans is of concern during winter, when small prey that is utilized by martens may be less available because of snowcover (Buskirk and Ruggiero 1994). Woody debris allows marten to access prey beneath the snow surface (Buskirk and Ruggiero 1994), and its loss along with the compaction of snow by vehicles may have negative impacts on marten populations by decreasing available food. LARGE CARNIVORES Grizzly bears in the GYA are effectively isolated from other populations. Maintenance of a stable or increasing bear population depends solely on reproduction by resident females (Knight and Eberhardt 1985). Most grizzly bear deaths in the GYA between 1973 and 1985 were human caused (both legal and illegal) and were clustered around gateway communities or other developments near Yellowstone National Park. Various attractants such as garbage, orchards, and outfitter camps tend to draw bears into conflict situations with humans, frequently resulting in bear mortality (Herrero 1985, Knight et al. 1988). Developments can function as population sinks for bears and other animals, potentially creating a drain on already stressed populations. Humans are responsible for most mortalities experienced by the newly reintroduced wolves in the GYA (Phillips and Smith 1997). Deaths occurred by collisions with vehicles, poaching, or management removals following wolf depredation on domestic livestock. Development on the borders of Yellowstone puts wolves in jeopardy if they travel outside of protected areas. Factors that stress ungulate populations, and thus increase their vulnerability to predation or other types of mortality, may benefit large carnivores and scavenger species in the short-term. However, if such factors lead to a long-term reduction of the ungulate populations, carnivore and scavenger species may be adversely affected through a reduction in the total amount of prey or carrion biomass available to them. OTHER SPECIES Little is known about the several owl species inhabiting this region (Holt and Hillis 1987), but owls may be particularly vulnerable to disturbance during winter when prey species are less vulnerable due to snowcover. Guth (1978) found that bird density and diversity increased in developed sites, but that the species present represented a greater percentage of common and widespread species; several rare forest species were absent. Amphibians, reptiles, small mammals, and fish are likely to be affected indirectly and more subtly by development and recreation than large mammal species (Cole and Landres 1995). Impacts to these smaller species, however, may have long-term impacts to overall wildlife community structure and function by altering prey base, plant community dynamics, and animal distribution (Gutzwiller 1995). MANAGEMENT GUIDELINES It has been stated that a critical role of parks and other protected natural areas is to compensate or correct for the influence of modern man on ecosystem processes (Houston 1982). Few wildlife populations in the GYA are restricted entirely to protected areas (Keiter 1991), however, and protected areas are also subject to pressures accompanying development. Many effects of development, such as removing winter range, blocking migration routes, disturbance caused by human activity, and reducing quantity or quality of forage species, carry particular impacts during the winter when animals are nutritionally and energetically stressed. In view of these observations, the following recommendations may help to reduce or mitigate the impacts of development on wildlife: * Minimize future development and, where possible, reduce current levels of development and their concomitant impacts in natural and protected areas. * Place any necessary new developments within or immediately adjacent to existing developments so that human impacts are clustered, allowing larger portions of relatively pristine habitat to remain intact. The location of future and existing activities and developments should be carefully considered to avoid disturbing or removing important habitat components. * Intrusive, noisy, or otherwise potentially disturbance-causing human activities should be avoided during the times of year when wildlife populations are already under severe environmental and/or physiological stress. Winter is a critical stress period for ungulates, and birthing/nesting time is critical for a wide variety of species. * Cooperation among adjoining land management agencies and with landowners adjacent to protected areas should be strengthened so that habitats spanning more than one jurisdiction are managed or conserved as intact systems. * Where possible, ungulate winter range should be protected or access acquired for wildlife to mitigate for existing development levels. * Research and monitoring programs on a wide variety of species are vital to accomplishing most of the recommendations above. Information on seasonal habitats, migration routes, nesting or birthing sites and areas, and timing of animal activities are necessary in order to avoid significant impacts of development on wildlife populations. LITERATURE CITED Anderson, C. C. 1958. The elk of Jackson Hole: a review of Jackson elk studies. Wyoming Game and Fish Commission Bulletin Number 10. Cheyenne, Wyoming, USA. Anderson, S. H. 1995. Recreational disturbance and wildlife populations. Pages 157?168 in R. L. Knight and K. J. Gutzwiller, editors. Wildlife and recreation: coexistence through management and research. Island Press, Washington, D.C., USA. Aune, K. E. 1981. Impact of winter recreationists on wildlife in a portion of Yellowstone National Park, Wyoming. Thesis, Montana State University, Bozeman, Montana, USA. Barmore, W. J. 1980. Population characteristics and habitat relationships of six ungulates in northern Yellowstone Park. Final report. National Park Service, Yellowstone National Park, Wyoming, USA. Buskirk, S. W., and L. F. Ruggiero. 1994. American marten. Pages 7?37 in L. F. Ruggiero, K. B. Aubry, S. W. Buskirk, L. J. Lyon, and W. J. Zielinski, editors. The scientific basis for conserving forest carnivores: American marten, fisher, lynx, and wolverine in the western United States. General Technical Report RM-254. U.S. Forest Service, Rocky Mountain Forest and Range Experiment Station, Fort Collins, Colorado, USA. Cole, D. N., and P. B. Landres. 1995. Indirect effects of recreationists on wildlife. Pages 183?202 in R. L. Knight and K. J. Gutzwiller, editors. Wildlife and recreation: coexistence through management and research. Island Press, Washington, D.C., USA. Dasmann, R. F., and R. D. Taber. 1956. Behavior of Columbian black-tailed deer with reference to population ecology. Journal of Mammalogy 37:143?164. Dunning, J. B., B. J. Danielson, and H. R. Pulliam. 1992. Ecological processes that affect populations in complex landscapes. Oikos 65(1):169?175. Garrott, R. A., G. C. White, R. M. Bartmann, L. H. Carpenter, and A. W. Alldredge. 1987. Movements of female mule deer in northwest Colorado. Journal of Wildlife Management 51:634?643. Glick, D., M. Carr, and B. Harting. 1991. An environmental profile of the greater Yellowstone ecosystem. Greater Yellowstone Coalition, Bozeman, Montana, USA. Glick, D., D. Cowan, R. Bonnie, D. Wilcove, C. Williams, D. Dellasala, and S. Primm. 1998. Incentives for conserving open lands in greater Yellowstone. Greater Yellowstone Coalition, Bozeman, Montana, USA. Goodman, D. 1996. Viability analysis of the pronghorn population wintering near Gardiner, Montana. Unpublished report, Montana State University, Bozeman, Montana, USA. Green, G. I. 1994. Use of spring carrion by bears in Yellowstone National Park. Thesis, University of Idaho, Moscow, Idaho, USA. Gunther, K. G., M. Biel, H. L. Robison, and H. Zachary. 1997. Administrative annual report for calendar year 1996. Bear Management Office, Yellowstone National Park, Wyoming, USA. Guth, R. W. 1978. Forest and campground bird communities of Peninsula State Park, Wisconsin. Passenger Pigeon 40:489?493. Gutzwiller, K. J. 1995. Recreational disturbance and wildlife communities. Pages 169?181 in R. L. Knight and K. J. Gutzwiller, editors. Wildlife and recreation: coexistence through management and research. Island Press, Washington, D.C., USA. Harting, B., and D. Glick. 1994. Sustaining greater Yellowstone, a blueprint for the future. Greater Yellowstone Coalition, Bozeman, Montana, USA. Herrero, S. 1985. Bear attacks: their causes and avoidance. Nick Lyons Books, New York, New York, USA. Holt, D. W., and J. M. Hillis. 1987. Current status and habitat associations of forest owls in western Montana. Proceedings of a Symposium on Biology and Conservation of Northern Forest Owls. General Technical Report Number RM-142. U.S. Forest Service, Rocky Mountain Range and Forest Experiment Station, Fort Collins, Colorado, USA. Houston, D. B. 1982. The northern Yellowstone elk. Macmillan, New York, New York, USA. Keiter, R. B. 1991. An introduction to the ecosystem management debate. Pages 3? 18 in R. B. Keiter and M. S. Boyce, editors. The greater Yellowstone ecosystem: redefining America?s wilderness heritage. Yale University Press, New Haven, Connecticut, USA. Knight, R. R., and L. L. Eberhardt. 1985. Population dynamics of the Yellowstone grizzly bear. Ecology 66:323?334. Knight, R. R., B. M. Blanchard, and L. L. Eberhardt. 1988. Mortality patterns and population sinks for Yellowstone grizzly bears, 1973?1985. Wildlife Society Bulletin 16:121?125. Lyon, L. J., K. B. Aubry, W. J. Zielinski, S. W. Buskirk, and L. F. Ruggiero. 1994. The scientific basis for conserving forest carnivores: considerations for management. Pages 128?137 in L. F. Ruggiero, K. B. Aubry, S. W. Buskirk, L. J. Lyon, and W. J. Zielinski, editors. The scientific basis for conserving forest carnivores: American marten, fisher, lynx, and wolverine in the western United States. General Technical Report RM-254. U.S. Forest Service, Rocky Mountain Forest and Range Experiment Station, Fort Collins, Colorado, USA. Mackie. R. J., and D. F. Pac. 1980. Deer and subdivisions in the Bridger Mountains, Montana. Pages 517?526 in Proceedings of the 60th annual conference of the Western Association of Fish and Wildlife Agencies, Kalispell, Montana, USA. Meagher, M. M. 1973. The bison of Yellowstone National Park. National Park Service, Scientific Monograph Number 1, Yellowstone National Park, Wyoming, USA. Nelson, E. W. 1925. Status of the pronghorn antelope, 1922?24. U.S. Forest Service Bulletin Number 1346. Nicholson, M. C., R. T. Bowyer, and J. G. Kie. 1997. Habitat selection and survival of mule deer: tradeoffs associated with migration. Journal of Mammalogy 78:483?504. NPS (National Park Service). 1998. Draft Environmental Impact Statement for the Interagency Bison Management Plan for the State of Montana and Yellowstone National Park. Publication D-655. May 1998. Phillips, M. K., and D. W. Smith. 1997. Yellowstone wolf project biennial report: 1995 and 1996. National Park Service, Yellowstone Center for Resources Report Number YCR-NR-97-4, Yellowstone National Park, Wyoming, USA. Rasker, R., and D. Glick. 1994. Footloose entrepreneurs: pioneers of the new west? Illahee? Journal for the Northwestern Environment 10(1):34?43. Robbins, R. L., D. E. Redfearn, and C. P. Stone. 1982. Refuges and elk management. Pages 479?507 in J. W. Thomas and D. E. Toweill, editors. Elk of North America: ecology and management. Stackpole Books, Harrisburg, Pennsylvania, USA. Skinner, C. K. 1922. The pronghorn. Journal of Mammalogy 3:82?105. Smith, B. L., and R. L. Robbins. 1994. Migrations and management of the Jackson Elk Herd. National Biological Survey, Resource Publication 199. Telfer, E. S., and J. P. Kelsall. 1984. Adaptation of some large North American mammals for survival in snow. Ecology 65:1828?1834. Thorne, E. T., M. Meagher, and R. Hillman. 1991. Brucellosis in free-ranging bison: three perspectives. Pages 275?287 in R. B. Keiter and M. S. Boyce, editors. The greater Yellowstone ecosystem: redefining America?s wilderness heritage. Yale University Press, New Haven, Connecticut, USA. Vogel, W. O. 1989. Response of deer to density and distribution of housing in Montana. Wildlife Society Bulletin 17:406?413. Wilcove, D. S., C. H. McLellan, and A. P. Dobson. 1986. Habitat fragmentation in the temperate zone. Pages 237?256 in M. E. Soule, editor. Conservation biology: the science of scarcity and diversity. Sinauer Associates, Sunderland, Massachusetts, USA. PREPARED BY: Wendy Clark, Wildlife Biologist, National Park Service, Yellowstone National Park, Wyoming, USA. Ron Wiseman, Wildlife Biologist, Beaverhead National Forest, Ennis, Montana, USA.

Keywords: animal, mammal, human activity, suburban area, Greater Yellowstone Ecosystem, Yellowstone National Park, Grand Teton National Park, habitat, population, mortality, behavior, livestock, grazing, ungulate, food, feeding, forage, predation, hunting, management, ecology, bear, grizzly bear, Ursus arctos horribilis, wolf, Ursidae, Canidae, Canis lupus, bison, Bison bison, coyote, Canis latrans, elk, Cervidae, Cervus elaphus, wapiti, moose, Alces alces, deer , mule deer, Odocoileus hemionus, migration, breeding, nest, nesting, whitetail deer, Odocoileus virginianus, Jackson Hole, Teton County, National Elk Refuge, Sublette County, winter food supplementation, disease , brucellosis, pronghorn, antelope, Antilocapra americana, marten, Martes americana, Lynx, Lynx Canadensis, Lynx lynx, Wolverine, Gulo gulo, Mustelidae, Felidae, Bobcat, Felis rufus, Bird, Ornithology, Aves, Owl, raptor, Amphibian, Reptile, Herpetology, Rodent, Rodentia, Squamata, Anura, Fish, Pisces